1. Field of the Invention
This invention relates generally to surgical instruments and, in particular, to surgical instruments having a plurality of components that are able to be locked together to produce a fixed structure. More particularly, the invention relates to a drill guide in which a cylindrical tube is slidable relative to a handle and is able to be locked to the handle in a selected position.
2. Description of the Prior Art
Drill guides are often used in surgical procedures in order to facilitate "blind" drilling by properly placing a drill relative to adjacent anatomical structures. A drill guide generally has a handle for holding the guide exterior to the body, a probe tip to be placed within the body at a point where one end of a drilled hole is desired and a tube which has its axis aligned to intersect the probe tip and which is slidable relative to the handle so that the distance between the end of the tube and the probe tip is variable. Drill guides are normally used in arthroscopic procedures by placing the probe tip through an arthroscopic portal, placing the tube end against a bone surface, inserting a drill into the tube and drilling through the bone until the drill comes out adjacent the probe tip.
One example of a prior art drill guide is shown in U.S. Pat. No. 4,739,751 (Sapega et al.). This device handle portion having a curved probe tip which is placeable at a specific location and a cylindrical drill guide attached to an arm slidable along the handle. The axis of the cylindrical drill guide intersects with the tip of the curved probe such that when the probe is placed within a joint during an arthroscopic procedure the placement of the cylindrical drill guide on the exterior surface of the bone enables a drill passing through the guide to intersect with the probe tip. Movement of the drill guide relative to the probe tip is a common feature of drill guides and is necessary to vary the distance between these two components to accommodate different bone thicknesses. Sapega et al. disclose that the drill guide arm may be attached to the handle by a ratchet and pawl mechanism to provide stability during drilling.
U.S. Pat. No. 4,708,139 (Dunbar, IV) discloses a similar arthroscopic drill guide which varies from Sapega et al. essentially in the means by which the drill guide arm is secured to the handle. Dunbar, IV shows a threaded knob passing through the handle and the drill guide arm. Rotation of the knob in one direction locks the guide arm on the handle and rotation in the other direction allows the guide arm to slide along the handle.
U.S. Pat. No. 4,920,958 (Walt et al.) discloses yet another drill guide assembly wherein the drill guide tube is locked to one end of an arcuate handle by a U-shaped spring. The drill guide tube is able to be pushed towards the probe tip without releasing the locking mechanism but is not able to be withdrawn without depressing the two legs of the U-shaped clip together.
Yet another known drill guide is manufactured by the assignee of the present invention and is part of the Concept Precise ACL Guide system. The precise tibial guide has a handle to which a probe tip and a drill guide arm are fixedly attached. The drill guide arm has a threaded aperture at its end and the drill guide is threadably secured in this aperture in alignment with the probe tip. A trigger mechanism on the handle releases the threads momentarily to enable the drill guide to be moved quickly longitudinally without rotation. Releasing the trigger engage the threads of the drill guide with threads in the end of the drill guide arm such that continued movement of the drill guide is only possible by rotation.
It has been found that all of the foregoing devices have features which could be improved upon. Most significantly, it has been found desirable to have a drill guide with an easier, single handed operating mechanism for releasing the guide tube to enable it to be moved longitudinally. It has also been found that, once the tube is in place, it is desirable to have a more secure holding device which prevents longitudinal movement of the tube.